Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 271112
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
712 AM EDT Wed Mar 27 2024

.SYNOPSIS...
A front will approach from the west today bringing increasing
chances for rain late Wednesday through Thursday before exiting
on Friday. Steadiest and heaviest rains are expected on
Thursday night, along with significant snowpack ripening or, in
the case of the coastal plain and adjacent interior,
significant snowpack melt. Precipitation may end as snow Friday
before things become drier and gusty over the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update...Showers have largely passed east of the forecast area
for the time being. I have added drizzle to the forecast thru
mid morning. After that point additional showers will likely
move into the forecast area from the west. Otherwise little
change to the previous forecast.

Previous discussion...S/WV trof is lifting thru the eastern
Great Lakes this morning...and is responsible for forcing some
showers moving thru parts of NH currently. To the east flow
remains onshore and occasional showers or drizzle continues in
that flow. To simplify the weather grids I have left wording
showery...as it will be damp either way.

With the trof driving into Quebec...the cold front will get left
behind and stall over the region. That will keep the threat of
showers and drizzle going thru the day today. It will also make
it difficult to scour out the cooler surface air...and I have
kept interior areas closer to a cold air dam for high temps.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Little movement in temps is expected tonight as the pattern
remains fairly well entrenched. Lows will be well above normal
for this time of year. Similar to today there will be the chance
for both showers and drizzle...but I will keep the wording
simplified with showers. Very late tonight precip character will
start to trend more towards steady rain as WAA increases
northeast of a developing low pressure off the Carolinas.

That low will track north along the stalled front and cross the
Gulf of ME Fri. The best forcing for ascent is still modeled
near the coast...and so the highest PoP and QPF remains there in
the forecast. With the mild air mass ptype is predominately rain
for all except the highest of high peaks.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Overview: A trough digs into the region to start the extended
period. It looks to phase with low pressure forming off the
coast of the Carolinas and stay overhead through much of the
weekend. This will keep the pattern unsettled, but high pressure
forming to the north may keep precipitation at bay.

Impacts: 1-2 inches of rain combined with snowmelt may lead to
flood concerns Thursday night into Friday, particularly in
coastal areas.

Details: Rainfall continues Thursday night as a front remains
stalled over the area. Most all models have recently come on
board with a progressive solution, suggesting the front gets
moving overnight just in time to push the low pressure system
that will be moving up the coast far enough offshore to keep the
heaviest rainfall out to sea. However, we will still be dealing
with a very moisture rich airmass with PWAT values 0.75 to 1
inch through the event. The latest available GEFS and ECMWF
ensembles suggest the coast could see 1-1.5 inches of rainfall
and the 00Z NAM likes amounts closer to 2-2.5 inches. Amounts
drop as you move inland with less than an inch likely northeast
of the mountains. Trends will continue to be closely monitored
as these numbers will be highly dependent on this interaction
between the front and the low. If the front doesn`t budge and
the low is allowed to come further eastward these numbers will
increase. It is also worth noting that we are 2 inches and
change from having the wettest March on record in Portland.

Precipitation will change to snow in the mountains heading into
Friday and then comes to an end Friday night. Cold air
advection looks to drop areas north of the mountains into the
20s while the foothills and areas south hover around or just
above freezing. At the same time high pressure building over the
southeastern U.S. looks to tighten the PGF which could lead to
strong wind gusts overnight heading into Saturday morning.
Saturday looks mostly dry, but low pressure offshore looks to
retrograde to some degree which could bring some light
precipitation to eastern zones. Otherwise, it looks to be a
pleasant but breezy day with highs ranging from the upper 30s
north to near 50 south. With mostly clear skies and a shortwave
ridge beginning to build in, temperatures likely drop into the
20s just about everywhere.

Sunday and Monday look dry as well as a shortwave ridge keeps
forcing associated with a wave ejecting off the Mid-Atlantic
coast well to our south. High pressure and a much more amplified
ridge build into the region Tuesday out ahead of our next
potentially significant system Tuesday night into Wedensday.
There is much uncertainty in just about every aspect of this
system so I won`t stray far from the NBM at this time range, but
snow lovers will want to be rooting for the GFS as it has
consistently been bringing us another block buster spring snow.
Other models favor rain, but either way this time period will
continue to be watched closely.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Fairly widespread IFR and lower conditions across
the area this morning...except for the far northern and western
zones where low level moisture has struggled to cross the higher
terrain. With little change in the overall pattern and flow...I
anticipate IFR or lower conditions will continue for much of the
area into Thu. TEMPO improvement is possible...mainly where
heavier rainfall can mix the atmosphere into Thu...but it is
expected to be short lived.

Long Term...IFR/MVFR conditions likely hold on through Friday
morning in most areas, but gradually improve from west to east
through the evening and overnight hours as precipitation comes
to an end and ceilings lift heading into Saturday. VFR looks to
prevail through Sunday. Gusty northwesterly winds may be upwards
of 30-35 kts Friday into Saturday low pressure tracks close to
the coast.

&&

.MARINE...
Short Term...Large swell continues on the coastal waters with
seas around 10 ft every 10 to 11 sec. Wave heights will
gradually diminish thru Thu...but are expected to remain at or
above 5 ft. I have extended the SCA thru midnight tonight...when
it is possible that seas beyond the islands of Casco Bay fall
below 5 ft.

Long Term...SCA conditions are likely through the extended
forecast period as a strong low pressure system tracks close to
the coast Friday night and Saturday. Northwesterly winds to gale
force are possible along with seas building to 5-7 ft.
Conditions begin to diminish on Sunday.

&&

.HYDROLOGY...
The snowpack is likely to melt out across the coastal plain
this week as periods of light rain and showers fall across the
area. River rises are expected, and some minor flood can`t be
ruled out by late this week and into the weekend. Areas further
inland and across the mountains can likely handle up to about
1.5" of rainfall, with most of this being absorbed by the
snowpack. Beyond that amount, runoff will begin to increase and
flooding would become a greater concern. The best chance for
exceeding this rainfall would come from a system passing
offshore on Friday. At this point the heaviest rainfall is
forecast to remain offshore, but this will need to be monitored
for any trends toward higher amounts, which would increase flood
concerns.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ150-
     152>154.

&&

$$

NEAR TERM...Legro
SHORT TERM...Legro
LONG TERM...Baron


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